Automatic gun compensator



' Sept. 2, 1947.

G. w. PONTIUS, 30.,- ETAl AUTOMATIC GUN COMPENSATOR Filed Jan. 23, 1942 8 Sheets-Sheet l NORMAL LINE 1; OF SIGH cousin-E0 LINE OF SIGH SIG-HT COEQECTION (LINE OF FLlG-HI'7 N w T u N P am a m m. ow 1 EAT FNfiN O O M5681 T m H A E MM E an M06 N u G M T O .T

AXIS OF AIRPLANE a &

' INVENTORS GEORGE W. PONTlUS- y AETHUE F. WILSON ATTORNEY Sept. 2, 1947. G. w. PONTIUS, 3D., ET AL 2,426,744

AUTOMATIC GUN COMPENSATOR Filed Jan. 23,- 1942 8 Sheets-Sheet 2 INVENTORS 65026:: W. Porn-nus m ARTHUR P. WILSON ATTORNEY,

P 1947- G. w. PONTIQS, an, ETAL 2,426,744

AUTOMATIC mm CQMPENSATOR FiledUan. 25,1942 8.She'ets-Sheet 4 INVE I Rs GEORGE W. PONTIUSN9 By AETHUE P. Wmso u)? ATTORNEY Sept. 2, 1947.

G. W. PONTIUS, 3D., EIAL AUTOMATIC GUN COMPENSATOR 8 Sheets-Sheet 5 Fil ed Jan. 25, 1942 u wm mm on. v I

INVENTORs- IIUS m GEQEGE W. PoN -BY AE-r'Huz P. Wn so- Sept. 1947- G. w. PONTIUIS, 30., ET AL 2,426,744

AUTOMAT I C GUN COMPEN SATOR 8 sheets-sheet 6 Filed Jan. 23, 1942 -v INVENTORS GEORGE W. Pow-nus m AETHUE P. WILSON murmur Sept. 2, 1947.

G. w. PONTIUS, 30., ET AL 5,

AUTOMATIC GUN CbMPENSATOR 8 Sheets-Sheet 7 Filed Jan. 23, 1942 INVENTORS 650265 W. PoN-rlus m BY AET'HUE P. WILSON ATTORNEY Patented Sept. 2, 1947 UNITED STATES TENT FHCE

AUTOMATIC GUN COMPENSATOR tion of Delaware Application January 23, 1942, Serial No. 427,904

8 Claims.

This invention relates to improvements in devices for the control of ordnance, and more particularly to the application thereof to military vehicles such as aircraft.

Armament for airplanes includes (a) guns which are freely movable in traverse and elevation relative to the plane upon which they are mounted, and (b) guns which are fixedly mounted in the wings or elsewhere upon the plane, and which therefore can be aimed only by aiming the plane.

The present invention relates generally to the latter type, but contemplates the provision of means for effecting a limited degree of movement of the gun in elevation to correct for varying angles of attack and range, as will be explained more fully hereinafter.

In military aircraft having fixedly mounted guns there are two problems in connection with their correct aim and fire to be considered. One is the problem of ever-changing angles of attack in flight, which is defined in this specification as the angle between the line of fiight and a longitudinal axis through the fuselage of an airplane. At extremely high speeds the longitudinal aXis may be inclined downwardly from the line of flight, and at other speeds may be inclined upwardly. Unless the guns are changed in response to this changing angle, it is obvious that they will fire at a point not corresponding to the target even when the airplane is aimed directly at the target.

The second problem is that of changing range of a target. Assuming that the guns can be adjusted to be parallel to the line of flight, upon firing of the guns the projectiles would not hit the target because their trajectory would cause them to fall upon a point below the target since gravity pull would be on the projectiles while in flight.

Now if the pilot raises the nose of his plane to take care of the problems above enumerated he soonthereafter loses sight of his target because the airplane begins to climb. This invention is a solution to both these problems and in an airplane equipped with a device incorporating this invention, the guns are automatically adjusted for the changes in angles of attack and changes in range of a target.

It is therefore an object of this invention to I provide means for correcting the elevation of guns for different attitudes of the plane and for different ranges of the target.

Another object of this invention is to provide a novel device for determining the range and making the determined range correction on the gun, so that the gun can be moved to the proper elevation for the correct angle of fire.

Yet another object is the provision of a novel construction which will automatically correct the position of the guns for variations in the angle of attack of the plane.

Yet another object is to provide a unique followup mechanism for use with a device for determining angle of attack which will be operable also to aid in determining the angle of elevation for guns for whatever range they are to be fired.

Still another object embraces the provision of a novel sighting device to be used as a part of this invention for automatically correcting the guns for difierent firing ranges.

Yet another object comprehends a construction which will provide an index or the like for a gunner or pilot which will enable him to obtain a range setting or elevation for all possible combinations of size and range of enemy aircraft.

Another object includes the provision of an automatic cutout construction which will render the guns inoperative when the sight is not in use, in order to prevent unnecessary expenditure of electric power, an important consideration in modern military aircraft, when so many accessories are dependent upon power' from a battery for operation.

Yet another object is the provision of an arrangement which will correct the sight to the line of flight, so that at all times the line of sight is parallel to the line of flight.

Still another object is to provide a construction making the automatic control inoperable, and returning the ordnance pieces to a fixed predetermined position, when the automatic compensation is not wanted.

Other objects of this invention will be more clearly understood after reference to the following drawings and description in which like numbers refer to like parts throughout. It is to be distinctly understood that the following description is illustrative merely of certain forms or embodiments, and that the invention may take other alternate forms without departing from the spirit of the invention, the scope and spirit of the invention 'being limited only by the appended claims.

In the drawings:

Figure 1, is a fragmentary isometric view showing a military airplane having mounted therein guns controlled and operated inaccordance with the present invention;

Figure 2 is a diagrammatic side view of the same; 7

Figure 3 shows a novel type of bridge circuit for controlling the elevation of the guns;

Figure 4 shows a schematic wiring diagram for compensating the gun for difierent angles of attack and diiiere'nt ranges. For simplicity, this figure shows the invention asapplied 'to'a single n;

Figure 5 shows schematically the inventionas applied to a plurality of guns;

Figure 5a shows the invention as applied to a plurality of guns driven by "asingle "j'ack'-motor through a mechanical linkage;

Figure 6 shows in section "a vane mounted in the leading edge of the wing for correcting the guns for different angles of "attack;

Figure 'I is a sectional view taken along the line 11 of Figure 6;

Figure 8 is a view taken along the line 8-8 of Figure 6 showing a novel "switching arrangement mounted in'thevahe; I

Figure 9 is "a 'plan view of the vaneshown in Figure 6 certain parts being in plan section to show the detaili'of a rack "and pinion arrangement' for operating the switch shown in Figure 8;

igure 10 shows in plan "certa'infelhiehts of the jack and operating meter for elevating and depressing "the guns, certain arts thereof being either shown in section or cut away; U I

Figure ll is a section taken "along the lines 1 I'H of Figure 10;

Figure '12 shows the 'nov' elfs ight arrangement forming ap'a'rt'o'i this 7 ion;

Figure 13 is a plan view talien al'ong the line -'|3 -'|31of-Figure'12; c I

Figure 14 'shovvs'f'a portion of "the film or tape of suitable materim 'used in triesig'ritshown in Figure "12 fdr determining the range and elevation;

Figure 15 is aseb'tibhalviivof'afspeii:rducmg arran ement foifl'ir'i akifig the Erie of sight parallel to the line (if ffiigh't as determined '53 the angle or attack vane; and

Figure '16 shows the image of an enemy aircraft positioned the sight. 7

Figures 1 and 2 sho'w'an airplane '30fihahattitude of horizontal flight. Although "the line of flight in such an attitudeishorizdntal,the longitudinal'akis of'the airplane may b e ihclihed at an angle to the "said line'of flight, either downwarclly, as shown, or ii'nder "other conditions upweirdl with guns rhountedinthewi'ng's"Beyond the reach of a gunner, "thle is no possibility "of hanging 'theirelevation to "compensate for this flight attitude. It becomes necessary then to provide a construction, either "rfianuallyor autoinatically operated for 'riiaintainih-g "the guns in proper eievauon.

f'T'he airplane shown nsur s 1 aria 2 ca-'rries wing mounteddrdhance pieces 32,"which'are controlled in "erevatidn by "an "angle '"of attack vane 3'4. 4

The angles through which the guns must be moved to place them in a position for effective firing ?is shown in Figure *2. The totalah-gle through which the guns ELTQ'IIIOVGdlS composed of two angles; one, the angle of attack, which places the guns in a position corresponding to the-line of flight of an aircraft; second, an angle corresponding to the range abrication, "which 'pla'ces the "guns in positionff e'ffective firing with re ard to a "r'afige as heterh'iiiied By the sight 36.

A simplified version of the electrical circuit for operating the various units of the invention is shown in Figure 3. With reference to Figure 3, there is shown a bridge circuit composed of an angle of attack potentiometer 45, which is mechanically connected to the angle of attack vane -34 s'hownin "Figure 1 Range variabl resistors Ml and 35 are 'inecha'nically -connected to, and

are controlled by the sight 36 shown in Figure l.

i l'gun jack potentiometer 48 in the other arm "of the :bridg'e'circuit is mechanically connected to the gun jack 40 shown in Figures 10 and 11.

The motor "42 is placed between the two arms of thebridge circuit, comprising on the one arm "variable resistors 44, G5 and potentiometer 46,

'which operates the gun jack 4t and which adjustable potentiometer 38 until a'balan'ce of the bridge is had, whereby equal amounts of potential difference will obtain in the two arms of the bridge circuit, so that no current "flows through the motor '42.

The complete electrical circuit is illustrated in Figure 4 where there is shown a source of power '54 connected to the circuit through a main power switch 56. The current takesa path through the field winding of a vfollow-up motor 58, and the flow of current through the armature windings of 'theffollowffup motor58 is controlled by means of relays'BU ah'd'62, which are energized loythe clo'sin'g'of circuits resulting from "the movement of switch cements cdntrolledjby the mowement of the angle "6f attack vane 34. The movement of the switchingelement'M is'accomplish'e'd throug a m a a l n w thea'n'gle'of attack vane '34. 'The switchtfi'c'omprises a flexible switching element which may close on'feof two circuitsatswitch Contact points 68 and in or switch contact points 12 and '14.

the'sofircefii' l through the switch '5Bf through a rotar limit switch iaythrough the rela to, and thence to ground at switch 66. Energi'zation of the 'reiay'su will 'rhove the armatures l6 andfilfl of the relay "60 thereby supplvih'g'curreht tothe armature winding of the follow-up motor "58, since aground is then maintained throughthe armature 82 of the relay 62. It will be s ee'nthen that the motor "58 'will rotat in follow-up according to the displacement of vane 34, so

that "the 'angle of attack potentiometer :46 'will be adjusted according to the flight attitudeof the 'aircr'aft 3'0. Similarily, through themedi-um of thefle xible cable 38, the sight 36 will be adjusted so that the line of sight 'is parallel to the line of flight. H V

However, when the switch contact isloroken at contact point 68 of the'switch B6 becauseof the 'rotationfo'f the follow-up motor 58 to which the Switch 66is connected "meehanianyjthe current flowing through the armature of the 'rh'otor '58 will not be out off since another ground is still 'made at the armature 16 of the relay 60. The

circuit when the motor is operating under this condition is through the ground at the switch 66, through the switch point I0, through the relay armature I6, and thence through the relay 60 to the source of current 54. When the follow-up motor 58, through appropriate gearing 84, has moved the switch to a position where the contact at point I is broken, the ground connection for the relay 6!] is also thereby broken, and deenergization of the relay 68 causes the relay armature 86 to close a connection at switch point 86 of the relay 60, and the armature winding of the motor 58 is thereby deenergized.

The circuit which is responsive to the movementof the angle of attack vane includes a follow-up construction for all movements of the angle of attack vane regardless of the direction. Assuming that the angle of attack vane 34' has taken a position whereby contact is made between a switch point I4 and flexible switching element 64, current will not flow in the line connecting the ground, switch point I4, and the armature 83 of the relay 62, until another contact has been made with the switch point 12 of the switch 64, resulting from a further movement of the Vane 34. When this second contact is made at switch point "I2 current will flow from the source 54 through the switch 56, through the limit switch 18, through the relay 62, and thence to ground. Energization of the relay 62 will move the armatures 82 and 83 whereby a ground is made for the armature winding of the follow-up motor 56, since a ground is then maintained through the switch point 86 of armature 86. Since the flow of current through the armature of the follow-up motor 58 is thereby reversed, the direction of rotation of the armature is also reversed. The follow-up mechanism comprising the motor 58 and the gearing 84, which is connected mechanically to the angle of attack vane 34, will then move to put the system in neutral once more as described previously. The rotation of the motor 58 will break a contact at the switch point I2, but the current flowing through the armature of the motor will not be cut off since another ground is still made at the relay armature 83 and the accompanying switch point. The circuit when the motor is operating under this condition is through the ground at switch 66, through the switch point 14, through the relay armature 83, throughthe relay 62, and thence to the source 54. The rotation of the motor will then break the contact at switch point I4 breaking the ground of the circuit comprising the relay 62, thereby breaking the source of current to the armature of the follow-up motor 58.

The follow-up motor 58, which is responsive in its movement to the movements of the angle of attack vane 34, is connected by a flexible shaft 38 to the gun sight 36, as shown in Figure l. The purpose of the flexible cable 38 is to provide for the correction of the sight 36 to the movements of the angle of attack vane 34. Since the angle of attack vane is responsive to the line of flight of an aircraft 36, it will, by means of the flexible cable 38, make the sight 36 responsive also to the line of flight of the aircraft 36. Appropriate gearing which will be describedwith reference to the details of the angle of attack vane and with reference to the details of the sight 36, will make the line of sight at all times parallel to the line of flight of the aircraft (see Figures 1 and 2).

When the follow-up motor has moved the switch 64 to the position where no contacts are made, the potentiometer 46 will have been adjusted to a position representing the condition of flight as determined by the angle of attack vane 34. The limit switch I8 is so arranged that current will not flow through the system above described when the angle of attack vane is beyond a position whereby correction can be effected. This construction provides a safety feature insuring against damage to the parts.

Thus far has been described a construction for placing a portion of an electrical circuit in a condition which will contribute to the efiect of another portion of an electrical circuit, whereby automatic compensation of ordnance may be effected. That portion of the system which varies the electrical circuit for the purpose described above will next be described.

Referring again to Figure 4, switch 96 controls the flow of current to the portion of the circuit which adjusts the position of ordnance for variations in range and size of an enemy aircraft and also for Variations in the angle of attack.

The switch 56, which is the main power switch for the circuit, controls the operation of part of the circuit which includes the novel sight construction forming a part of this invention. The sight includes a source of light I38, which can be cut off entirely through a manual switch I40, and which can be adjusted in its intensity by means of a manually operated rheostat I42. The

sight also comprises a film driving mechanism shown schematically in this figure (Figure 4) and an optical system not shown in this figure but described below.

A construction is provided whereby the gunner or aviator can remove the effect of the angle of attack and range correction of portions of the circuit from the ordnance pieces. This construction eliminates small movements of the guns which would normally be efiected by the angle of attack follow-up construction when changes in the flight attitude occur. The switch is operated manually to negate the control effect of the sight and angle of attack follow-up construction whenever their operation is not wanted. When the manual switch 90 is closed, the balancing portion of the circuit shown in Figure 3 is broken, and the ordnance pieces are returned to a fixed position as determined by an index switch I 2I mechanically connected to the gear drive located at the gun jack 46, the details of which operation Will be explained later in this specification.

A pair of switches are operable to control the speed of film movement through the sight and also its direction. Control of the motors which drive the film in the sight is as follows. When a manually operated high speed switch I44 is closed to either one of its two switch points cur-. rent will flow through the armature of a film drive motor I46, through the series winding I48 of said motor, and thence to ground. Reversal of the direction of the motor I46 is accomplished by throwing the switch I44 to the other switch point, the motor I46 having a field winding I56 of opposite direction. A bufier resistor I4! is provided between the source 54 and. the armature of the motor I46 to control its starting torque. The line drop develop-ed by the resistor I41 prevents any tendency for the motor I46 to start abruptly which might possibly do damage to the film. When the motor I46 is operating at high speed, a relay 92, disposed in the circuit which controls the movement of the gun jacks 40 is energized, thereby breaking the circuit at armature 94 of the relay 92, The breaking of this circuit prevents se'ives to cut off the eurrem to the p-aft of the c'i'iuit which I tipei' ates' 'the *Grdnance ipiece's when the "-g unh'er 6r EIViEtUI' is changing f-rbm enewing spanef al'n enem aircraft Ito another Wingispan. when 1 the circuit is 'ccimple-ted at the xshdtch d 60, the re1a3y 98 is thereby :energi 'z'ed. 'I-he relay armature 96 then breaks the circuit at that point, sio that no current 'czin flew 'to' the pertf the ii-it whichcentrolsthe mdvemeiit of the=ord- -n nce. V

Wheh the Sight has been -eiiijusted 'for the proper ranges emu -Size'df an'e'nem' aircmft the 'Ciif'ri'itWil-l then teike a- 'path thrbu'g-h the Switches "56, 94mm? S 'S'tHrOiiEh the rzngefireriabie resistor 44 to the angle of attack potentim-ter =45, thrbu'gh' said potenticmeter, thence' through fange variable resistor '45 and thence to g'roimd. The

ofcurr'ent through-this circuit-is the' equiveeeeph 'rfe'nfliheiy now flew fr'om the sources! through '-theW it6h l-ZZftl'ihCB to*'a.--Wi'1iding 1Z4 iii-a fies wound machine gun jack motor 42; through the armature 128 ='o'f the motor 42 and th'e'n'ce to g'rcii'n'd. The clo'sing of the doiible po1e's Witch [-22 "also energizes "a 'wind'ing ffl forming -a part 6f *2. magnetic clutch in connection with the motor '42. -'Engagement of the clutch or the indtbr causes 'gearing $32 on the ja'ck i4!) 450 turn 'in-s'uch a men'n'e'r either to elevate the guns or impress the-m, depending upon the directien of the field current"-ii'i 'the-motor 42.

The gearing 132 is ccnnec'ted -mecha;riiGe3I-1-y to the wiping arm- 0mm potehtiemete'r 18 (Figure 3') end ine-wipin arm "of the'pbteriticmet-er will move to a position whichwiil bailaii'ce the bridge, thereby stopping the fiow of current ti'ire'ilfg h"the polar relay 52. Thepolar relay-armature flw will then e'ccup a neutral pos'iticn between the switch points l I' U =and' l i 2 and the "relay l18" wi11 thenfbe -deenergized eridtheSWitch I'2-2 -wi11 open. The-energi'zationbf the 'field winding '-l24,-'and the magnetic clutch winding P3Wwi11tlrfenciaasle, and the 'g'earing Will be brought to an abrupt stop through "the 'rnediu'm-- (if a friction brake lo'cated i'n=connection With the-ihagnetic c1utch, ntit-shdwn in 'Fi'gii're'4. I

As'suming that "the flow 0f ciirre n't through the polar relay '52 is reversed, "the p'cilar relay armatuie' F8 9 williriaike contejctat switchicmint l-N). A

pole s-witch 1'38 -will close. Cu'rren't'wiir-now flo'w fro'r'n the Source 5 tirir'cugh both p'dles Of the switch F3 6, and the magnetic clutch windih-g will thereby be energized et the *selmetime as the fifeld win'iiihg 38a -*of the meter- 42v "The'field Winding 438w is wound in an -c ippesite di'r'ec'tion from that 0f the field' wihdirig 1 2 1 h'r'iE-thediiec- "the}beiancingporticn df the bridge ciicilit'hown "'efiefg'i zed, and the aim eture -r-z's w111 =retateto fndve the guh to a neiitfali positicn. Uponqeiosin l2 I ave rita'et' les euhreiit wiil fio te emergize'relay i-fli which eausesmcterm t rotate 1 in theep-po'si te direction tereturn the gii'n to neu- Hire-1. meeha'rii'cel a'rrahgemem es'secidted 'With the 'gir tifive F312; fcr 'c'pe'reitirig the gim jack 40, will move the index switch to a position whereby switch elements I23 and I25, associated with the index switch I2I, will fail to make contact. Failure of the switch elements I23 and I25 to make contact at the index switch I2 I will thereby deenergize the windings I36a, I24, I30, associated with the gun jack motor and the magnetic clutch. Thus the operation of the switch 98 and the indexing switch I2I returns the guns 32 to a fixed position relative to the aircraft 30.

The limit switch I29, associated with the gearing I32, for driving the gun jack 40 is so arranged that when the guns reach a determined position the operation of the jack motor 42 will be suspended. When limit switch I 20 has rotated to a position where the cutout sector I3! spans switch element I29, relay II8 will be deenergized: similarly, rela I34 will be deenergized when the cutout sector I3I spans switch element I21. The incorporation of the two switches I20 and I2I in the system shown in Figure 4 provides a double safety feature, which insures against the guns reaching a position whereby danger to any of the parts might occur,

The detailed description of the angle of attack vane will be had with reference to Figures 6, '7, 8 and 9. In Figure 6 is shown in section a portion of the leading edge of the wing 36 of the airplane shown in Figure 1, having mount-ed therein the angle of attack vane 34 enclosed in a housing I62. The interior end of the housing I62 is rigidly connected to a switch-enclosing housing I64 which isattached to the airplane wing 30. Connected to the housing I64 is a gear case I66 containing a worm I 68 and a wormwheel I which is driven by th follow-up motor 58 described in Figure 4 and shown in Figure 7. The adjustable angle of attack potentiometer 46 is shown mounted adjacent the gear casing I66. A shaft I72 connects potentiometer 46, the wormwheel I19, and the follow-up portion of the switch 56. The follow-up portion of the switch 66 carries the switch points 68, I0, I2 and I4, described in Figure 4, and shown also in Figure 8.

The angle of attack vane 34 is attached to a pivot I14 which carries an arm H3 having a rack I78 which engages a pinion I80 mounted at the end of the shaft I82 located within the housing I62. Suitable bearings I84 and I66 mounted in the housing I62 support the shaft I32, the other end of which is connected to the switch element 64.

With reference to Figure '7 there is shown the follow-up motor 58 which is secured to the gear casing I66. shaft I6'I carrying the worm I68 which drives the worm-wheel I18. Attached to the shaft I61 is a flexible shaft 38 which turns in a sheath I90. The flexible shaft is connected at its other end to a speed reducer unit shown in Figures 12 and 15.

In Figures 12 and there is shown a speed reducer which is contained in a housing I92, rigidly secured to a portion I96 of the aircraft structure. The driven end of the speed reducer is contained in a cup-shaped member I93 which is bolted to the sight 36, pivotally mounted at I 94 to the portion I96 of the aircraft structure.

The speed reducer end of the flexible shaft 38 is attached to a driving shaft I98, containing gears 200 and 202, which turns in suitable bearings located within the housing I92. One end of the shaft I38 and the end of the flexible shaft 38 is enclosed by a nipple 204' threaded to the housing I92. The'gear 202 drives a gear 209 which rotates in a suitable bearing mounted in the hous- The follow-up motor 58 drives a axial movement on the shaft 208 by a nut 220 I threaded to the end of the shaft 208, and is pivotally mounted inany suitable manner in the member I93.

The operation of the speed reducer shown in Figure 15 is as follows. Since gear 200 is larger in diameter than gear 202 the speed of rotation of gear 206 will be less than that of gear 2I0. The difference in relative rotation of these two gears will thereby cause the shaft 208 to move axially,

with respect to the housing I92, depending upon the direction of rotation of the shaft I98. It will be apparent that the axial movement of the shaft 298 will effect a rotative movement on the sight 36, shown in Figure 12, since it is pivoted at I94. Selection of the proper gearing shown in Figure 15 will cause the sight 36 to be rotated through such an angle that the line of sight will at all times be parallel to the line of flight of the aircraft. 7

The sight which has been described with reference to Figure 4, will now be described in detail with reference to Figures 12, 13, 14, and 16. The sight 36 comprises a casing 222 which is pivoted at I94, and whichis made to rotate by the axial movement of the shaft 208, the outer end of which is fixed in a housing I93 as previously described. An L-shaped tube 224 is secured to an opening in the casing 222, andpolarizing media 226 and 228 serve to limit the ingress of light to the tube 224. The amount of light which can enter the tube 224 is varied by rotation of one of the polarizing media'with respect to the other.

The casing 222 has within it a light source I38 which is suitably prevented from emitting stray light by a shield 230. A film drivemotor I46 is suitably'mounted in the casing 222 and drives a sprocket 232 mounted on a shaft 233, by gearing not shown, to effect the movement of a film 234 between a screen 236 and a ground glass guide plate 238. Proper tension is maintained on the film at all times by helical springs 240 and 242 located respectively in film reels 245 and 241. Disposed in the tube 224 are a pair of collimating lenses 244 and 246. A substantially transparent glass screen 249 is disposed at an angle of to the line of sight of the aircraft 30, and also at 45 to the'beam of light transmitted by the light source I 38, which passes through the film 234 at the screen 236 and through the collimatin-g lenses 244 and 246.

The film 234 is shown in detail in Figure 14 but actually is opposite to the black and white relationship shown. In other words, the body of the film is opaque, and the lines and figures thereon are substantially transparent. The numbers near the upper edge of the filmstrip 234 and adjacent the sprocket drive holes, represent the Wing span of an enemy aircraft as measured in feet. The numbers near the lower edge of the film strip 234, and adjacent the sprocket drive holes, represent the range of an enemy aircraft in hundreds of yards. The film strip 234 is shown with a center line 248 and a pair ofdiverg- 11 ing lines 250 located symmetrical-1yv with respect to-the. center line 248, disposed one on each side.

of the center linev 248'.

Figure 13 shows the plan view oiithe screen no A. shutter: 23] is. provided in the'pathof they I light. rays. comingthrough .the screen 236.- to pre:

vent blurring of the figures representing the. wingv span of an enemy aircraft? when theymovepast the. screen 236; By appropriate gearing (not shown) a slot inithe shutter 23:! ismade to coincide with the figures. representing the'wing span, so'thatthey appear stationary to the operator;

A shaft 233; upon which the'film' sprocket drivev is mounted, drives the range. variable resistors 44 and 45, not shown in Figures 12' andl3r, which make one completerevolution during the; move.- meritv of one set of diverging span lines past. the screen 236: and the guide. 238.

In: Figure 1 6: is. shown the image; of an enemy aircraft. 252 positioned between the sight lines 259: shown in; Figure-14. The aviator has: selected the portion of the filmproperly applicable to, a.

size of wing span shown in feet at the left of the? image shown in. Figure: 16; At. the: right is shown the. range in hundreds of yards along the sight. linev 2.50..

The operationof the system shown. in. Figures- 12; I3, 14 and 16" is as follows. The light rays from the source I38 pass. through theground.

glass guide. plate 23%, through the transparent;

portions of the film 234 and the screen 2 36',

through the collimating lense 2'44 and1246, and. are reflected. from the glass screen 249 to the eyes of an aviator or gunner 254. The gunner places the center line ot'the enemy aircraft 252' in superimposition with the center" line- 248' of the filmstrip- 234:. He then effects movement of the film strip through the guide138- by close ing either switch M4: or switch L52; shown: in' Figure. L, to;- the position of the: film which has a wing span. marking corresponding to' the wing spam. of theenemy: aircraft 2152.. By varying the speed and: direction of the. film by means of switches I44? and: I 2: he is able to keep the image of the. enemy aircraft located at all times within the range lines 25il shown in'F-igure 16;

It will be seen that the movement of the film strip; 23!!- in the. sight. 3.6 varifeszthe: setting of the variable; resistors 44: and 4'5, and that. when. the stadia. lines; 25!) are spanning: the: target image, there; is; created an unbalance: of the bridge. circult to. pass current through the. polar relay" 52: to-movethe guns ,3-2 untiLbymeans of g-unipotentiometer 48, the bridge is again ba1anced.. When the condition of balance ofthe bridge is had, the guns 32 are. properly-v trained on the target for-a particular flight. attitude of airplane 31), for a particularsize target, and for a particular range oftarget'.

Inn Figures and Il3therevis shown theldetailed I construction of the gun jack referred to in thedescription hadwith'. reference to Figure 4'. The gun jack 49 comprises a casing 254" which. is secured; to:- a. portion: 256: of; the aircraft structurn. itsbase, is a, bearing 258 for; receiving the end: of. ajack worm-wheel 260. The bearing; 258' is Located: Within: the; casing 254; and near- 12. disposed between. a shoulder inthe casing. 254; and, a shoulder 282 on: the worm-wheel .260 The casing 254 is closed partly at itsupper. extremity by a plate 264' having a flange which protrudes.

intothe: casing, and. is secured to the casingt by cap bolts 2661. In: the. recess between the worm-- wheel 260 and the flange, portion of the. cover. plate 264 ispositioneda bearing'268, and shoulders located on the worm-wheel 260. and the flange portion of. the cover. plate 26 prevent the. axial. movement of both bearings- 268 and the wormwh-eelzfiii. A small. circular plate: 210- is; secured.

to the cover. plate. 264 and. closes the: circular opening between the. cover plate 264 andthe-drive wormewheel 260..

The worm-wheel 2.60 hasan interior threaded.

surface which is engaged by a squarecutscrew' 212. The end of the screw-2T2 is formed into. an eye 214 through which a pinv 216* is passed, and; which pin is also passed through eyes 2'18 disposed. at the end of an ordnance piece 32;. The

worm-wheel 260 is driven by thefgunjackmotor 42 through a magneticclutch comprising a winding I30. The control of the operation; of the I motor 42, and of the clutch has been described previously with reference to Figured. When the motor 42 is operated, the winding I" is at the same time energized. The movement of the driven member 218. to. the right in Figure 10 is opposedbya spring biased element2'l1 and spring 2l9. Deenergization of. the winding I310 causes. thedriven portion 218 to act as a brake, since when it' is urged to the left, it will be frictionally engaged by a surface. 281 in the" housing of the motor 42. Energizationof thewinding I30 causes a driven portion 218 to be pulled'to the right, where it is engaged by the driving end of the armature I28 of'the motor 42: The driven meme ber 218: is slidably mounted on a splined portion 280 of. a driving shaft 282 which? is rotatablymounted at each end in suitablebearings 2'84. located in the casing 254; The driving shaft.v 282 has a worm 28.5 mounted. thereon, which drives. the worm-Wheel 2601 The worm-wheel 26U'has anexternallythread'ed portion 288 which engages by'a spur 290, mechanically connected to the gun potentiometer 48, the

index switch 12 l', and the limit switch I20, which have been described with reference to Figure. 4, by a shaft 294 mounted in bearings 296* located in the casing 254-, and which arecontained in a suitable housing 292.

The operation of the arrangement shown in Figures; 10 and 1 1 is as; follows. When the motor. 52 is operated the clutch will engage the arm-ature 12% sincewinding I30 will be; energized.v The turning: of therarmature I28 of. motor; 42 drives therworm 286 which effectsrotation of. the wormswheel 2610.. Rotation of thee wormewheel'. 2611'. causes: rotation of the: spur: 290 which is err-- gageol:v by the externally threaded: portion: 288' of the worm-wheel: 260.. system. will. remain: operable untill the: spur 29.0? and. its associated. shaft 29 4 changes: the position. of. thegun'. potentiometer; index switch. l2flr, and. limit switch: until the bridge-circuit: be'balanced, or untilthe index. switch. [21' makes; the; guns; immovable. when. the: bridge circuit is. made inoperable.

Wit-h reference to: Figured there is shown the system as outlined above. in connection with. aplurality of: ordnance pieces. In. the figure.- the reference numerals: refer to equivalent parts; as: describedwithzreference:tdtheforegoing; description-. I'm the. system. shown. in Figure 5 it will be seenthat one angle: of attack vane: 34.-will con- -v tribute to the control of the system, and that one sight 35 and the range variable resistors 44 and 45 included therein will contribute to the control of the guns. However, the balancing of the circuit is effected by incorporating a separate polar relay and separate gun potentiometers associted with each ordnance piece. The operation of the system shown in Figure 5 is identical with that described with reference to the foregoing descriptions.

In Figure 5a there is shown a system in which a single motor 42 isused for driving the gunjacks. The gun jack' motor 42, which has been described with reference to a single ordnance piece, as shown in Figure 4, now effects the drive of all of the ordnance pieces through a set of gears 300. A flexible shaft 302 connects the gear train 300 and a driving gear 394 associated with each gun jack.

It will be seen that this construction makes unnecessary a motor associated with each gun jack, a single motor 42 in the control circuit as described with reference to Figure 4, effecting the control of a plurality of ordnance pieces. This construction makes'necessary the use of only one polar relay 52 and only one gun potentiometer 48. It will be seen also that the field control relays H8 and I34 will be associated only with the master control motor 42, making unnecessary their use in connection with each gun.

The operation of the invention is as follows.

When the pilot of the airplane 3i] wishes to have automatic compensation of the guns 32 for both range and angle of attack, he closes power switch 56 which passes current to the field of the followup motor 58 of the angle of attack vane 34. Assuming now that the vane 34, which adjusts itself according to the line of flight of the airplane 39, closes switch 66 at contact points 68 and 16, current will then flow through the rotary limit switch 18, through the relay 60 and thence to ground at the switch 66. When the relay is energized, relay armatures It and 80 will close to supply current to the armature of follow-up motor 58 to open switch 66, and stop motor 58. The angle of attack potentiometer 46 will then be adjusted according to the position of the angle of attack vane 34, and the sight 36 will be rotated slightly, by means of flexible shaft 38, so that the line of sight is parallel to the line of flight.

The pilot meanwhile has sighted on an enemy target plane, and knowing the wing span of the enemy target plane, he adjusts the movable film strip 234 until the stadia lines 258 are tangent to the wings of the target image 252 as seen in the sight 36. The movement of the field strip 234 at the same time adjusts the range variable resistors 44 and 45 to a position corresponding to the corrected range.

The portion of the bridge circuit embracing the angle of attack potentiometer 46 and the range variable resistors 44 and 45 will cause a potential difference between the wiper arm of angle of attack potentiometer 4S and gun potentiometer 48 to actuate the polar relay 52, which determines the movement of gun jack motor 42. The guns 32 will then move in follow-up as determined by the condition of angle of attack potentiometer 45 and range variable resistors 44 and 45. As the guns are moved in follow-up, the gun potentiometer 48 will be adjusted to a position where no potential difference will obtain to actuate polar relay 52 thu cutting the current to the gun jack motor 42, at which. time the guns 32 will be adjusted for both range and angle of attack, whereby they are correctly trained on any enemy target.

Thus there has been described a construction for automatically compensating ordnance for all attitudes of the vehicle wherein they may be mounted, and for all conditions of range in which they may be fired. There has also been described a novel construction which includes the use of safety devices so that danger to the parts thereof will not be experienced when an aircraft assumes a flight attitude which will not permit of compensation of the ordnance.

The constructions described are desirable embodiments of invention, but it is not to be construed that the invention is limited to the embodiment shown, the limitations being only'ac-,

cording to the terms of the claims appended.

What is claimed is:

1. The combination with a gun mounted on an aircraft, of means including an air vane mounted on the aircraft and arranged to follow the line of flight of the aircraft, sighting means mounted on said aircraft for viewing a target and including means for determining the range of the target, means mounted on said aircraft and drivably connected to said gun and sight for elevating and depressing said gun and sight relative to the aircraft, and means'controlled by said firstnamed means and the means for determining the range of the target for compensating the gun for range and angle of attack.

2. Apparatus for controlling a gun mounted on an aircraft, comprising means mounted on the which are here aircraft and operatively connected to the gun for elevating and depressing said gun relative to the aircraft to compensate for angle of attack of said aircraft, control circuits for said means, and

, means mounted on said aircraft and disposed'in the air stream to follow the line of flight of the aircraft, said control circuit including means responsive to said last-named means for connecting said control circuits to said first-named means to elevate or depress said gun.

3. Apparatus for controlling ordnance mounted on an aircraft, comprising a gun mounted on the aircraft for movement in elevation and depression relative to the aircraft, a sight for said gun. constructed and arranged for movement in elevation and depression relative to said aircraft and to said gun; means drivably connected to the gun for elevating and depressing the same,means' mounted on the aircraft and having a member disposed in the air stream to follow the line of flight of said aircraft, a motor operative in response to said member as it follows the line of flight of said aircraft, control circuits connected to said first-named means and to said motor, means connecting said motor to said sight for moving the sight to compensate for the angle of attack of the aircraft, and means in said control circuits responsive to rotation of said motor for creating an unbalanced condition in said circuits to cause said first-named means to elevate or depress said gun.

4. The combination with a gun and sighting means therefor mounted on an aircraft, of means including an air vane mounted on the aircraft and projecting into the air stream to follow the line of flight of the aircraft, means including a reversible motor operatively connected to said sighting means and responsive to movement of the vane for controlling the position of said sight in elevation and depression relative to the aircraft, and means including a reversible mow iter t e y nn c e s said sun nd; 2 sponsive to rotation of said f1rst.-.named motor r con ro i h 95 2 h sun: n elevai h and er s h s.c mp n fe a e f a t is- A m ahis his 011iroi ingv he ele atio of, a gun with respect to. an aircraft on which the gun is mounted, to, compensate for the angle of attack 01 the aircraft, so that the gun Will be page s the es i i ht 9 h aim i sing an emi nt projecting into the wind stream and constructed and arranged to move to a position corresponding to, the line of flight f said a ai as he lesf tta h varies, n electrical system tor controlling the elevation of the gun to. compensate foran'gle, of attack and including a device drivably connected to said gun, and means in said system responsive to movement of said element forenergizing said system to operate said device.

6. A mechanism for elevating and depressing a gun with respect to an aircraft on which the gun is mounted to compensate for the angle of attack ofthe aircraft, so. that the gun will be parallel to. the line of flight oi the aircraft, comprising an element projecting into the wind stream, and constructed and arranged to move to a position corresponding to the line of flight of said; aircraft, an electrical system for controlling said gun and including a follow-up motor and a potentiometer controlled in its movement by said motor so as to introduce an unbalanced condition into said system to cause a change. in elevation of said gun, and. means in said system responsive to the. change in position of the element, as the angle of attack changes for connecting said system to the gun and responsive to the follow-up. motor for disconnectns a d ys em f om. the u Z. A mechanism for controlling the elevation oi a gun with respect to an aircraft on which e gun i moun d to om ns e o e angle of attack of the aircraft, so that the gun bore will be parallel to the line of flight of the aircra t co isin n lemen r tin in o t w nd stre m an con t ucte nd ar an ed to arliu its t a o it on q r s esnd ne is h ine of f i t of h ai sra an el tr a s s e r c n ro l n aid 9 m a d ncluding a fol p m t r and potentiomet sshi l s ts ovement. by a d me er o ni ed ci s h 1hhalansed ndit on to s id ystem for s sin a chang in. s sv tie o said she, a d me n n aid, s s em hav n one member resp n iv t he. h pes iii p s ion i t e el me t as e a gels f ta of. said a rc a t han es nd a second member responsive to, rotation of the muss-1 p m ist a euceead arranged, to be enga ed by movement of said members respectively connect as. i sqehs t ai e ec r cal em i from said. gun, for changing its elevation.

8. A m chanism for, chan ing the position f a ii slsva ea r t e s n i c which the, gun is mounted, comprising an electrical control system having means" therein for connecting the system to the gun at times when a han e; in heel iiatin r he un. i desired and for disormectihe the system r m he un;

whenthe un has e mov to a predetermined by the he is m v d s, a p ede erm ed s t h. ele ati n aid first member, so that GEQ QE W-, FQNTIUS shee-N neFEaENons one!) The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name D t 1,862,919 Barnes June 14;, 193.2 2,254,611 harnhart May 26, 1942 2,173,656. Newell se t. 19, 1939 2,047,727 Dueringer f July 14 1926 10 1 4352 Trautmann Dec. 29, 19 36 2,153,516 el; Apr. 4, 1939 9411248; pe a 51, 1924 1,724,093. rg u h et al. A g. 13, 1929 1,939,517 Paulus et a1. Dec. 12, 1933 1,474,74fi Walker et al Nov. 20, 1923 1,329,131 Bates Oct. 27, 1931 19191191 B s -.-v---- Jul 5', 19.3 2, 60,202 Fieux May 30 1939 2,190,569 Macgill Feb. 13, 1940 OR GN T N S,

Number Country Date 127,026 Great Britain May 29, 1919 800,484 France Q. May 4, 1936 817,228 France May 21, 1937 

